The Algorithm Choice: Deconstructing the Two Brains of the SCUBAPRO G3

In the world of high-performance dive computers, vibrant color screens and smartphone connectivity have become the expected standard. The real differentiator—the “brain” of the device—is the decompression algorithm. For serious divers, the logic that governs their ascent profile is the single most critical feature. It’s a matter of trust, philosophy, and physics.

The SCUBAPRO G3 Wrist Scuba Dive Computer steps directly into this high-level conversation. It is a tool built for the experienced, technical, and professional diver, evident in its stainless steel construction and modes for Trimix, CCR, and Sidemount diving.

But its most defining feature is a fundamental choice it presents to its owner: which “brain” do you want to use today? The G3 is one of the few computers on the market that houses two distinct, powerful decompression philosophies based on the legendary Bühlmann ZHL-16 model. This isn’t just a minor setting; it’s a choice between two different ways of managing decompression risk.

Understanding this choice is the key to understanding the G3 itself.

Philosophy 1: The “Adaptive” Model (ZHL-16 ADT MB PMG)

This is Scubapro’s proprietary, “trust the machine” approach. It takes the baseline Bühlmann ZHL-16 algorithm and enhances it with several complex, dynamic layers. Let’s deconstruct that alphabet soup:

• ZHL-16: The foundation. A robust model developed by Dr. Albert A. Bühlmann that calculates inert gas loading in 16 theoretical “tissue compartments,” from fast-saturating (like blood) to slow-saturating (like dense cartilage).
• ADT (Adaptive): This is the core “smart” feature. The algorithm adapts its calculations based on your measured behavior. It can factor in exertion (almost certainly requiring a paired SCUBAPRO heart rate monitor, sold separately), water temperature, and ascent rate. If it detects high workload (a rapid heart rate), it assumes increased gas loading and makes the profile more conservative.
• MB (Microbubble): This layer addresses the theory that decompression sickness isn’t just about dissolved gas, but also about tiny, asymptomatic “silent bubbles.” This model adds conservatism to limit the growth of these microbubbles, particularly on repetitive dives or ascents, by modifying the maximum tolerated gas pressure (M-values).
• PMG (Predictive Multi-Gas): This is a critical technical diving feature. It allows you to program up to 8 gas mixtures (like high-oxygen Nitrox or Trimix). It predicts your entire decompression schedule based on your plan to switch to different gases during your ascent, optimizing for the most efficient off-gassing.

Who is this for? This algorithm is for the diver who embraces Scubapro’s ecosystem. It’s for the advanced recreational or technical diver who wants the computer to make real-time, conservative adjustments based on their actual, measured physiological workload.

Philosophy 2: The “User-Control” Model (ZHL-16 GF)

This is the “trust your plan” approach, which has become the gold standard in the technical diving community, largely popularized by competitors like Shearwater.

• ZHL-16: It starts with the same 16-tissue Bühlmann model.
• GF (Gradient Factors): This is the key difference. Instead of a proprietary “black box” of adaptive logic, Gradient Factors give you direct, granular control over the algorithm’s conservatism. You set two numbers, GF Low and GF High (e.g., 30/85):
  • GF Low (30%): This controls your first, deepest decompression stop. A low number forces a deeper stop, getting you off the “bottom” faster to begin off-gassing slow tissues while limiting bubble formation.
  • GF High (85%): This controls your final stops near the surface. This number dictates how much “residual” gas tension you are willing to have when you surface.

This model is not adaptive; it is prescriptive. It will execute the exact 30/85 profile regardless of your heart rate or workload. Technical divers favor this because of its absolute consistency, which allows them to perfectly match their computer’s plan to their desktop dive planning software.

Who is this for? This is for the technical diver, the CCR diver, or the sidemount diver who meticulously plans every aspect of their dive. They don’t want the computer to “adapt”; they want it to execute their plan flawlessly.

The fact that the G3 offers both is its most powerful statement, catering to two different but equally valid expert philosophies.

The Physics of Air Integration and RBT

The G3 package includes the Smart + Pro transmitter, enabling wireless air integration. This technology is about more than just eliminating a hose.

A traditional pressure gauge (SPG) only tells you how much air you have (e.g., 1500 PSI). This is static data. The G3’s processor takes that pressure reading and combines it with your current depth and real-time gas consumption rate to calculate True Remaining Bottom Time (RBT).

RBT answers a far more important question: “How many minutes can I stay at this specific depth before I must begin my ascent?” This is a dynamic, actionable piece of safety data that an analog SPG simply cannot provide.

However, this technology relies on low-frequency radio waves to transmit data from the tank to your wrist. Underwater radio transmission is notoriously difficult. Signals are line-of-sight and can be blocked by the diver’s own body or other equipment. A brief “lost connection” (as mentioned in one user review) is a known physical limitation of all hoseless systems. Divers are trained to wait a moment, adjust their arm position, and allow the signal to re-acquire, a minor trade-off for the advanced RBT data and streamlined profile.

First Principles: Hardware and Readability

A computer’s “brain” is useless if its display is unreadable. The G3 is built on a foundation of robust, first-principle hardware design.

• Display: It features a high-contrast, full-color display with a backlight. Objectively, this technology provides superior readability in all conditions—from dark, murky water to bright sunlight on the surface—compared to older monochrome screens. It allows for logical color-coding of critical data, such as warnings, so the diver can process information at a glance.
• Housing: The robust stainless steel housing is a clear mark of a premium, “built-to-last” device. This is a significant step up from the plastic or composite housings of many computers, giving it the durability to achieve its 300-meter (984 ft) depth rating in Gauge Mode.
• Tactile Backup: The G3 includes a stainless steel rotatable timing bezel with luminescent markers. This is a brilliant nod to classic dive watch design. It provides a simple, tactile, and battery-free method for timing a dive in Gauge mode or tracking a safety stop, serving as an invaluable analog backup.

Conclusion: A Tool for the Educated Diver

The SCUBAPRO G3 is not just another dive computer. It is a sophisticated instrument that demands a high level of understanding from its user. Its primary value proposition lies not in its color screen, but in the fundamental, philosophical choice it offers between two of the most respected decompression models in the industry.

It is a tool built for the technical expert who wants to fine-tune their Gradient Factors and the advanced recreational diver who wants to leverage adaptive biometrics. By integrating powerful software with a robust, stainless-steel, multi-mode hardware platform, the G3 establishes itself as a serious contender for the diver who has moved beyond simple data and is ready to take conscious, educated control of their decompression philosophy.